The recording density of magnetic recording apparatuses is expected to achieve Tbits/inch2 in the future due to the development of perpendicular magnetic recording methods and magnetic head techniques using current-perpendicular-to-plane giant-magnetoresistance (CPP-GMR) elements and tunneling magnetoresistance (TMR) elements. In order to improve the resolution in the bits-per-inch (BPI) direction (the track length direction), the gap between shields should be narrowed. However, narrowing the gap is difficult since there is an element formed of various layers such as an antiferromagnetic layer, a magnetization pinned layer, a nonmagnetic layer, and a magnetization free layer between the shields.
In order to improve the resolution in the track-per-inch (TPI) direction (the track width direction), the track width or the element size should be reduced. However, the reduction in element size may cause heat. Therefore, the element preferably has a low resistance and a high output. However, reducing the resistance of the TMR element and increasing the output of CPP-GMR element are difficult. As a result, reading heads of a Tbits/inch2 level have not been obtained yet.
Reproducing heads using the spin accumulation effect have been proposed to solve these problems. Such heads, however, are difficult to increase output.
The applicant has filed a patent application for a reading head using the spin accumulation effect, which has a high output. As will be described later, the filed reading head has a problem in obtaining a good crystallinity in the nonmagnetic layer and the magnetic layers, and has a difficulty in controlling the degradation of the spin diffusion length in the nonmagnetic layer and the degradation of the polarizability in the magnetic layers.
Therefore, the compatibility is important between the design of the element structure for having advantages over conventional spin valve elements and obtaining a low resistance and a high output and the crystallinity of the nonmagnetic layers and the magnetic layers.